SMTP is the Simple Mail Transfer Protocol, the most recent standard of which is defined in RFC 5321. It's the Internet standard for sending and receiving email.

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Email sent from my new server, being suspended by SMTP because “weird” hostname?

I have some problems sending emails from my server: I've been banned/suspended for abuse (IP blocked) by the SMTP server. This happens only on my new virtual server. Right to the question: is my new ...
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0answers
58 views

SMTP - Apache SOLR - Localhost to Server

I'm developing a single page application (ajax-php-mysql) using XAMPP (localhost). The app needs to be able to send out quite a few emails per day, not anything crazy like 100,000 but I do suspect it ...
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3answers
637 views

Is blocking SMTP ports prevent server from sending emails?

I have a Centos server with cPanel on it. Yesterday, some hackers had successfully connected to my smpt server and sent thousand of emails from it. What I want to do is blocking every ports except ...
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1answer
296 views

smtp relay attack on our mail server (not an open relay server)

Help, We put our Exchange Server (10.0.0.125) behind a SMTP Proxy server (Xeams if you have heard of it), however recently our client complaints we replies their email too late - and we found ...
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1answer
86 views

Random synchronization error on SMTP server

We can send mails across the network from 1 server to another via a centralized smtp server. However, the we get a synchronization error on the server randomly. So for example if we send a simple ...
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1answer
105 views

SMTPD restrictions

i'm looking for a bit of advice on Postfix restrictions configuration. I'm looking for a balanced configuration which properly rejects spam and unauthorized access retries. Lately, i've been reading ...
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2answers
763 views

Google blocks authentication attempts by my machine to transfer outgoing mails [closed]

I am using gmail as SMTP server (via ssmtp mail transfer agent in Ubuntu 12.04) for sending outgoing mails from my server. But the problem is that Google often blocks authentication attempts by my ...
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1answer
99 views

Postfix does not reject wrong client and HELO name

I have a postfix server configured with reject_unknown_client_hostname and reject_unknown_helo_hostname. Regardless the server accepts non sasl_authenticated connections from clients and HELO names ...
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1answer
110 views

SMTP Connection disconnecting after “STARTTLS”

We're having issues with our mail server. Basically some emails from external networks are not being accepted by the mailserver. After some debugging using telnet and looking through the logfiles, it ...
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1answer
144 views

change ehlo name of Amavis

Server: Ubuntu 12.04 64 bit Setup Postfix + Dovecot + Amavis with Mysql for Virtual domains. I have configured the postfix mailserver successfully. However when I test the Email with mail-tester.com, ...
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2answers
438 views

How to stop or prevent Postfix / smtpd / Sasl brute forcing

There are numerous attempts to connect to my mail server in order to send mail either unauthenticated or to guess username and password to, I suppose, accomplish the same. Should I fight against ...
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1answer
36 views

What is the correct way to get an NDR to be sent when a bounce back occurs?

I have a user who developed a WebApp that sends SMTP messages. Users are able to reply to the message using a MUA (outlook, whatever) but there is no NDR if the user doesn't exist. I suspect that ...
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0answers
959 views

Office 365: 'client smtp submission' suddenly starts failing. How to diagnose client auth error?

Since a few days, my application fails sending SMTP email. The app is in fact a scheduled task (which is running on my local machine, written in C#, using SmtpClient) and occasionally needs to send ...
2
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1answer
76 views

How easy is it to sniff the SMTP port of webserver to capture mails

I've got a very basic question that I don't know the answer for. Our company owns a webserver that runs multiple websites and works as a mail server for these websites as well (e.g. to send contact ...
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1answer
104 views

SBS 2003; Exchange 2003 can't receive mails without SMTP connection but without POP3 connector [closed]

i hope you can help. I'm losing my mind. I'm not a specialist in SBS but i have a huge problem. I wanted to replace the mircosoft pop3-connector with popcon because i was told that several mails ...
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2answers
88 views

Correct FQDN Setting?

I can see from SMTP logs that some mail is being rejected OutboundConnectionResponse SMTPSVC1 Sxxx - 25 - - 504+:+Helo+command+rejected:+need+fully-qualified+hostname 0 0 69 0 47 SMTP In ...
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1answer
94 views

Where does e-mail header “Received: from…” come from? [closed]

I sent myself an e-mail from my server to my gmail account, here is one of the headers (partially redacted): Received: from cpvds3xx.xxx.com (dev1.xxx.com. [209.51.132.xxx]) by mx.google.com ...
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2answers
652 views

Why is email being delivered normally despite an SPF “hardfail”?

I'm trying to figure out why forged email is being delivered to major email providers (gmail.com, outlook.com) even though email is marked with an SPF hardfail. The email is also delivered to ...
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1answer
322 views

hMail delivery queue full with unsuccesfull spam

Since a day or two the mail delivery queue of the hMailServer is exploding because someone is trying to send spam via this server. Though the e-mails aren't successfully sent it fills up the mail ...
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1answer
59 views

Is extra “Received by” in mail headers bad and can I remove it?

I use our own VPS web and mail server to send out a newsletter regularly to 50,000 addresses. I am trying to improve deliverability and was looking through some of the thousands of bounce emails. One ...
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1answer
33 views

Scanning server results in warning about STARTTLS [closed]

After scanning our webserver, I've got this message: The remote SMTP service, support the user of the 'STARTTLS' command to switch from a plaintext to an encrypted communications channel. As I ...
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2answers
1k views

Exim on Centos - Configuring gmail smtp

I want to set up Exim to send the mails through my gmail (actually my domains google apps). I have added the router, transport and authenticator. Specifically: gmail_route: driver = manualroute ...
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0answers
258 views

Configuring Monit to Send Mail through Office365

I'm trying to configure monit to send emails through Office365. Here's the relevant configuration: set mailserver smtp.office365.com port 587 username "username" password "password" using ...
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0answers
135 views

Undeliverable SMTP email not saved to badmail folder using IIS6.0

I am testing my SMTP virtual server hosted in IIS6.0 to verify that when an email cant be delivered and cant be sent back to the sender, then I need to see a copy of the Non Deliver Report in the ...
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2answers
93 views

Email flagget as spam or rejected by recipient mail server

I have configured smtp service on a windows 2008 server. All the emails sent by the smtp service are flagged as spam or they are rejected by the recipient of the email. In the header of the email I ...
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1answer
184 views

Using alternate server for specific subdomain - DNS settings

I'm trying to set up DNS records for a domain name, such that mail.domain.com uses a server that is different from any other request to *.domain.com. As I've been going about trying to figure out how ...
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0answers
3k views

550 5.7.1 Message Rejected due to content restrictions

I have a server that for some reason, out of the blue is now having a huge amount of its email being rejected, coming back with 550 5.7.1 NDR's or various derivatives thereof. This just started ...
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0answers
141 views

Handing E-mail Bounce Back in IIS, Setting up SMTP

Our servers send e-mails from @example.com to customers, clients, etc. We use Google Apps for our domain to send and receive additional e-mails from @example.com. Now, we're trying to handle e-mails ...
2
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1answer
6k views

Postfix - Host or domain not found

I just installed Postfix on my ubuntu, on a local network. On this network, I have an Exchange Server (using domain mail.example.com). I had a problem sending an email to a local address : ...
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0answers
23 views

IIS SMTP deleting messages that failed to send

Windows Server 2008 R2 with IIS 6.0 SMTP I recently ran into a smarthost permission issue where my IIS mail server couldn't forward certain messages to it. Basically, the user authenticated for the ...
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1answer
211 views

Send email through Gmail SMTP to avoid local delivery attempts?

Background We use Google Apps for email with our domain example.com: [ec2-user@example ~]$ dig MX example.com … ;; ANSWER SECTION: example.com. 300 IN MX 1 ...
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1answer
98 views

Restrict SMTP for localhost only

How can we restrict SMTP service to be used on localhost only? Our websites are using localhost SMTP but we do not want any mail clients to use our server on SMTP port. Our server is Windows Server ...
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2answers
399 views

Domino always server fails to send SMTP email at first attempt

In our logs, we find the below: Router: No messages transferred to fakedomain.com (host mx.fakedomain.com) via SMTP: The server is not responding. The server may be down or you may be experiencing ...
2
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1answer
290 views

Unable to Connect to SMTP Host

I am trying to configure Postfix on CentOS 6 server, and the problem is that I cannot receive mails. I tested it on http://mxtoolbox.com/ and I get an error Unable to Connect to SMTP Host. I check ...
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1answer
146 views

What are the security risks with running an SMTP server? [closed]

I'm running Windows Server 2012 and I would like to set up an SMTP server to work with my hosted websites. I've previously installed various roles on my server which have resulted in exposing security ...
0
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1answer
179 views

Postfix mail from outside not received

I am using Dovecot with Postfix and virtual user/mailboxes. Everything works fine accepting receiving mail from outside (other domains named as the mailserver) I am able to: - send mail from my mail ...
6
votes
1answer
163 views

Should I listen for SMTP on both 25 and 587?

I was setting up haraka as our mailing server, and for outbound email, it suggests moving to port 587 for SMTPS auth support. However, I'm unsure if I should be running 2 instances of haraka on ...
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1answer
1k views

CentOS postfix smtp server connection refused from outside

I am quite stuck with my postfix/smtp configuration on my CentOS machine. I setup a mail dns mail.domain.tld, configured in the postfix main.conf file and tested locally on the server by connecting ...
2
votes
1answer
73 views

SMTP routing cases: same @domain as sender and different @domain

I would like to know what is the difference between sending an email to the same @domain as the sender and sending to a different domain. I cant really find a detailed explanation on the web. From ...
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1answer
90 views

Postfix only delivering mail locally (instead of correct destination)

For whatever reason, postfix cannot send email to my google apps account. It says the message is sent, but I've confirmed with google apps support that the message isn't being received. (Thus it is ...
0
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1answer
133 views

Exchange 2007 rate limiting

I have devices on the network that send out email alerts for misc things. The other night there was a condition that caused one of the devices to send a few thousand emails to a couple of internal ...
0
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1answer
299 views

check_smtp not working when scheduled

I am trying to set up a new check in Nagios 3.5.0, making sure that my mail server is contactable on port 25 over the internet. I am using the check_smtp command. When I run this command from the ...
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1answer
209 views

postfix deliveries per connection

hope you can assist me in this case. I am administrating an Postfix server which is used for newsletters. Recently one of the major recipient domains changed their policies to only accept one email ...
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0answers
43 views

Issue with Russian Characters using IIS6 SMTP Relay

We have an issue where we have an issue with Russian Characters in the body of emails when using IIS6 SMTP Relay on Windows Server 2008 R2. The relay points to an email provider. The characters ...
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0answers
65 views

Using mime_header_checks to ACCEPT instead of REJECT?

I'm pretty well versed in using header_checks/mime_header_checks to refuse smtp mail in Postfix, but now I think I've gone off the path of righteousness; I'm trying to suss out a way that I can refuse ...
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0answers
111 views

Outlook on Exchange: Why does it mangle return address for some email?

We have seen this too much in multiple Exchange environments, and need some guidance. When we email (using simple mail client app) to certain Exchange/Outlook sites, when those sites hit Reply, our ...
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0answers
90 views

SMTP on Windows Server 2008

Okay, i know that the built in SMTP server role inside Server 2008 is a little beleaguered; however, using resources here (stackex) and from msft I've worked through the issues I've been able to ...
0
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1answer
177 views

What do I need to be able to send mass SMTP email efficiently? [closed]

I am creating a web application that allows users to send broadcast emails to a list of subscribers. Essentially, it's a mass emailer and autoresponder, like AWeber or Constant Contact or MailChimp. ...
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0answers
7 views

Limit esmtp authentication on courier mailserver to certain IP addresses

I would like to limit authentication for users outside of our company network. It is possible to block authentication based on networks or by selected users? Thank you for any tips.
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1answer
182 views

5.7.1 relay access denied when accessing from vb.net application

I am developing a program in vb.net which needs to connect directly with my mailserver (postfix) to send emails which will be directed towards email to sms transmissions. My mailserver is otherwise ...